Keynote lecture
Decoupled water splitting for green hydrogen production: From breakthrough research to developing new technology

Green hydrogen produced by splitting water molecules into hydrogen and oxygen (water electrolysis) using electricity from renewable energy sources such as solar and wind is essential to reduce greenhouse gas emissions, especially in hard-to-abate industrial sectors such as steelmaking and ammonia production. It is a critical component in the energy transition to fight climate change, which is estimated to contribute above 10% of the global energy demand in future Net Zero scenarios. To this end, the production cost of green hydrogen should drop from above $5/kg today to below $1/kg to compete with fossil fuels. This requires reducing the cost of electrolyzer from above $1,000/kW to below $200/kW and improving their efficiency from 70% to 90% and above.

To adress these challenges, we developed alternative processes that decouple the generation of hydrogen and oxygen into two consecutive stages (time separation),¹ or two cells (space separation),² avoiding the need for expensive membranes and sealing in water electrolysis. In addition, we divided the oxygen evolution reaction, a difficult electrochemical reaction that requires the concerted transfer of four electrons and protons on a single atomic reaction site at the surface of the anode to generate an oxygen molecule, into two sub-reactions that occur on four sites, thereby enabling facile reactions and reducing the lion`s share of the energy losses in water electrolysis. An ultrahigh efficiency of nearly 99% was demonstrated at lab scale (100 mW),² and we expect reaching ~95% at system scale (1 MW). To bring this breakthrough research to reality we established H₂Pro, an Israeli startup company that aims to produce green hydrogen at $1/kg by the end of this decade, based on our invention.³

References:

1. Nature Materials 16, 646–651 (2017).

2. Nature Energy 4, 786–795 (2019).

3. United States Patent No. 2020/0040467 A1 (2020).